JS Sort Function

I have a JS/ASP application that sorts a SQL populated table.
This works great, and sorts the data fine, apart from my currency columns.
It wants to read the data as text as far as i can gather. Ths data in ASP
looks like this -
<% =formatcurrency(RS("income"),2)%>
I have tried changing this to a number (formatnumber) and hard coding a £
sign, yet it still wants to read the data as text, rather than numerical?
How can i get my JS function to read currency or if not, eliminate the
forehand figures. I need the data to appear as a currency, yet be sorted as
a number (rather than taking the 2st digit)if this is a
common problem (sorting currency) and there was a universal solution around
this